1. Field of the Invention
This invention relates to equipment for refueling aircraft at airports.
2. Description of the Related Art
Major airports are frequently constructed to have large-capacity underground supply systems for aircraft fuel. Access to the supply systems is by way of hydrants located below the airport surface but accessible from the surface of the airport. The hydrants are equipped with flow-control valves under the control of the operator of the refueler vehicle.
A refueler vehicle of the hydrant type includes the following: a fuel hydrant hose and means for coupling the hydrant hose to the hydrant; a pressurized air hose for coupling to the hydrant valve for controlling the open and close positions of the hydrant flow control valves, the air hose controllable by the operator from a remote position; at least one fuel delivery hose with a coupling to the aircraft intake valve; means for coupling the hydrant and delivery fuel hoses, including filtering and metering equipment; and a platform or deck for supporting the operator. Refuelers are discussed in U.S. Pat. No. 4,886,282, issued Dec. 12, 1989 to Wilkinson et al., which is incorporated by reference for its teachings on hydrant refuelers.
To accommodate different aircraft models having different wing heights, refuelers have typically included an elevator platform on which the operator stands when he connects the delivery fuel hose to the tank valve beneath the wing and during fuel delivery. The elevator platform may be of the scissors type. Elevator platforms have the undesirable feature of being prone to jamming or otherwise disabled, particularly in sub-freezing weather.
The Wilkinson U.S. Pat. No. 4,886,282 circumvented the problem of elevator platform failure by providing multiple non-elevating type platforms within the range of commercial wing heights. The non-elevating platforms offer greater mechanical reliability than the elevatortype, but lack the convenient continual height adjustment which is possible with elevator type platforms.
Other failures in previous hydrant type refuelers are due to gas engine and power train problems. If the engine or power train fails, the entire refueler is rendered inoperable. It is known to separate the power module from the hydrant refueler, in a fashion analogous to the separation between the tractor and trailer in truck designs. Such a hydrant refuelers are referred to as a "fixed hydrant cart" because, once they are towed to their destination, they are deployed in a normally fixed position. Maneuvering a tractor with a fixed hydrant cart attached in a congested area near a plane requires a great deal of skill. For this reason, airport authorities have typically chosen mobile hydrant carts, and have accepted the disadvantages of risk of engine and drive train failure, and added EPA exhaust emissions in airports as preferable to the risk of injury and property damage which may occur using fewer tractors and fixed hydrant cart arrangements.